Item 9B. Other Information.

Insider Trading Arrangements Intended to Satisfy the Affirmative Defense of Rule 10b5-1(c)

During the three months ended December 31, 2025, two officers of the Company entered into trading plans intended to satisfy the affirmative defense of Rule 10b5-1(c) of the Exchange Act (each such trading plan, a "Plan"), as discussed below.

On November 14, 2025, Cynthia Cann, Chief Accounting Officer, entered into a Plan that provides for the sale of up to 3,986 CoStar Group Shares. Ms. Cann’s plan terminates on July 31, 2026, for a duration of 259 days.

On December 4, 2025, Michael Desmarais, Chief Human Resources Officer, entered into a Plan that provides for the sale of up to 5,000 CoStar Group Shares. Mr. Desmarais's Plan terminates on July 31, 2026, for a duration of 239 days.

During the three months ended December 31, 2025, no other directors or officers, as defined in Rule 16a-1(f), adopted or terminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” each as defined in Item 408 of Regulation S-K.